1. Field of the Invention
This invention relates to crushing machines. More particularly, this invention relates to a crushing machine that crushes scrap, such as plastic scrap, between the wall of a casing and crushing blades which have a predetermined thickness and which are mounted on a rotary shaft. In addition, the present invention relates to a method for cleaning the crushing machine.
2. Description of the Related Art
In an injection molding operation, pieces of scrap accumulate in the sprue and the runner. The pieces of scrap are crushed by a crushing machine, in which at least one crushing blade is turned, and then are recycled and mixed with the raw material little by little.
In an injection molding operation, sometimes it is necessary to switch the raw material with another or to replace the metal mold with another. In this situation, the crushed material is removed from the interior of the crushing machine (i.e., the crushing machine is cleaned).
A conventional crushing machine is cleaned as follows. A compressed air hose is inserted into the crushing machine through a material charging inlet or a material discharging outlet and applies compressed air to remove the crushed material. Alternatively, the casing of the crushing machine may be removed to apply compressed air to the crushing blades and the wall of the casing.
When the injection molding operation is restarted after switching the raw material, the crushed material that accumulated before the crushing machine was cleaned is discharged. Thus, after the crushed material is removed from the crushing machine, the crushed material is not used or recycled.
In addition, during the manual cleaning of a conventional crushing machine, a significant amount of the crushed material may not be removed. Furthermore, the manual cleaning operation is disadvantageous because it takes a relatively long period of time to perform and because the compressed air may scatter dust around the interior of the crushing machine.
Also, since the crushing blades are rotatably provided in the casing, there are gaps between the wall of the casing and the crushing blades. Therefore, when rotating the crushing blades crush plastic scrap into small pieces, the crushed material becomes caught in the gaps. Since, it is impossible to apply the compressed air directly to the gaps, the crushed material is liable to remain in the gaps even if the interior of the crushing machine is cleaned.
Accordingly, when the injection molding operation is restarted, the crushed material must be discharged for a long period of time in order to ensure that all of the old crushed material is removed. Consequently, the production efficiency of a conventional crushing machine is low. In addition, the crushed material which has been discharged cannot be used again, and therefore, there is a problem in handling and discarding the material.
Recently, a crushing machine has been combined with an injection molding machine such that the crushing machine is operated in conjunction with the injection molding machine. However, the cleaning operation can only be performed when the injection molding machine is not operating. Accordingly, it is inefficient to perform the manual cleaning operation for a long period of time. Therefore, an object of the invention is to provide a crushing machine which can be cleaned within a short period of time and in which the amount of crushed material remaining in the crushing machine after it is cleaned is minimized. Another object of the invention is to provide a method for cleaning the crushing machine.